Gaseous fuel burner and control therefor



Jam 23,, 1951 R. E. YATES ETAL GASEOUS FUEL BURNER AND CONTROL THEREFOR6 Sheets-Sheet 1 Filed Nov. 12. 1947 1X a w w y Jan. 23, 3951 R. E.YATES ETAL.

GASEOUS FUEL BURNER AND CONTROL THEREFOR Filed Nov. 12, 1947 6Sheets-Sheet 2 9 1951 R. E. YATES EI'AL 2,538,952

GASEOUS FUEL BURNER AND CONTROL THEREFOR Filed Nov. 12, 1947 6Sheets-Sheet 3 I. I Y

Jan 2,, 11951 R. E. YATES ETAL GASEOUS FUEL BURNER AND CONTROL THEREFOR6 Sheets-Sheet 4 Filed Nov. 12, 1947 1776 1 11 f0l-$ foer'f E yrlfs 0.km g w? 4; .1 Ma a m id Z W 1 a W Jan. 1951 R. E. YATES ETAL 2,533,952

GASEOUS FUEL BURNER AND CONTROL. THEREF'0R Filed Nov. 12, 1947 6Sheets-Sheet 5 6 Sheets-Sheet 6 gel Ilia/I2 apex/2e Z l a w; I Z 0 2 R.E. YATES ET AL GASEOUS FUEL BURNER AND CONTROL THEREFOR Jan. 23 1951Filed Nov. 12, 1947 Patented Jan. 23, 1951 GASEOUS FUEL BURNER ANDcommon maaroa Robert E. Yates, Joseph M. Engel, and William W. Riesche,Chicago, Ill., assignors to Drying Systems, Inc., Chicago, 111., acorporation inois Application November 12, 1947, Serial No. 785,488

7 Claims. (Cl. 158-99) This invention relates to gas burners and thesafety control thereof, and particularly it relates to such burners thatare adapted for safe operation in a rapidly moving current of air.

Where gas burners are used for ordinary purposes, the air supply thatmoves past the burner is, in most instances, maintained at the absoluteminimum that is consistent with attainment of complete combustion of thegaseous fuel, but where such burners are utilized in drying apparatussuch, for example, as domestic clothes driers, it is desirable that thegas burner be placed directly in the path of the rapidly moving currentof air that is forced through the clothes drier so as to thereby heatsuch air. In the past it has been impossible to attain this desirablelocation of a gas burner in a rapidly moving current of air that isrequired in a clothes drier or the like, and as a result, in thosedriers equipped with electrical heating means, the cost of operation ofwhich has been objectionably high. It is, therefore, an important objectof the present invention to enable a gas burner to be safely utilizedwhen disposed in a rapidly moving current of air such as the air thatisforced through a clothes drier or the like, and an object related to theforegoing is to enable this to be accomplished with a gas burner ofextremely simple construction. A further and related object of thepresent invention is to provide a gas burner that will operate safelyand efliciently when disposed in the path of a rapidly moving current ofair, and a related object is to provide such a burner and controlassembly that is unitary in its arrangement so that it may be readilyplaced in the air supply duct of a domestic clothes drier or the like toheat the air passing through such duct.

It will be evident, of course, that where a gas burner is utilized in adomestic clothes drier, the operation of such burner must be renderedextremely safe, and it is a further object of the present invention toprovide control means for such burners so that such safe operation maybe attained. A related object is to provide a control means operating onan electronic principle, and so constructed and arranged that it may beeconomically utilized in controlling the gas burner of a domesticclothes drier or the like.

Other and further objects of the present invention will be apparent fromthe following description and claims and are illustrated in theaccompanying drawings which, by way of illustration, show a preferredembodiment, and the principles thereof and what we now consider to bethe best mode in which we have contemplated 2 applying those principles.Other embodiments of the invention embodying the same or equivalentprinciples may be used and structural changes may be made as desired bythose skilled in the art without departing from the present inventionand the purview of the appended claims.

In the drawings:

Fig. 1 is a vertical sectional view illustrating one form of domesticclothes drier in which the gas burner of the present invention has beenincorporated;

Fig. 2 is a vertical sectional view taken substantially along the line2-2 of Fig. 1, and illustrates further details of the burner and themanner of its association with the clothes drier;

Fig. 3 is a plan section taken substantially along the line 3-3 of Fig.1and illustrating the burner and a part of the control means on anenlarged scale;

Fig. 4 is a view taken from the line 4-4 in Fig. 3 and illustrating therear or inlet end of the burner;

Fig. 5 is a fragmentary sectional view taken along the line 55 of Fig. 3and illustrating the outlet end of the burner;

Fig. 6 is a plan section taken along the line 6-6 of Fig. 3;

Fig. '7 is a developed view illustrating the arrangement and proportionsof the air inlet and other openings of the main burner;

Fig. 8 is a side elevational view of one form of electrically controlledfuel valve that may be used;

Fig. 9 is a somewhat diagrammatic vertical sectional view showing thevalve of Fig. 8;

Fig. 10 is a schematic wiring diagram illustrating the control circuitof the present invention; and

Fig. 11 is a fragmentary wiring diagram showing another form of ignitionmeans.

For purposes of disclosure, the invention is herein illustrated asembodied in a burner and control unit ID that is incorporated as theheating means in a domestic clothes drier unit I l.

, The clothes drier l I that is herein shown is somewhat similar in itsgeneral arrangement to the clothes drier shown in Broglie Patent No.2,424,737, patented July 29, 1947, and this drier includes a casing I2,the upper front wall of which includes an upwardly and rearwardlysloping portion I28, and in this sloping portion I2S a loading openingI3 is afforded so that clothes may be inserted downwardly and rearwardlythrough an aligned loading chute M to fall into a rotatably andgenerally cylindrical drying drum [5 3 thatisdisposedwithinthecasing |2.Thedrum II is supported primarily on a bearing structure I. carried onthe rear wall of the casing- I2, and this drum has a relatively largeforward opening I! that is aligned with the chute l4. vanes IIV disposedat spaced points and in inwardly extending radial'positions within thedrum serve to assure an eillcient tumbling action of the clothes as thedrum rotates.

Within the casing |2 and in outwardly spaced relationship with respectto the cylindrical walls of the drum It, a stationary inner housing 2.is afforded so that drying air may be forced into and confined withinthe inner-housing 20 as it passes through and about the drum ll. Suchair is heated as will hereinafter be described and is circulated aboutthe drum l and into the drum through perforations 2| that are affordedin the cylindrical wall of the drum. The inner housing 2. is sealed orconnected as at 22 to the inner end of the chute |4 so that the dryingair will be properly confined and such drying air may, of course, passinto the chute 4 but is normally retained therein by a door 24 that maybe placed over the loading opening I: during the drying operation. Thedrying air is supplied to the inner housing by a blower 25 that ismounted on a horizontal axis within the casing l2 at the inlet of ahorimental duct 26 that is formed within the casing l2 and beneath thelower wall of the inner housing 2|, It is within this duct 26 that theburner unit II is mounted, and the drying air is forced from the fan orblower 25 past the burner unit ill and then upwardly at the right handend of the duct 20, as viewed in Fig. l, and into the inner housing 20through an inlet opening 28. Such air is thus heated by the burner unitl0 and passes through and about the drum I5 and then is forced out ofthe inner housing 2|! through an outlet duct 29.

The fan 25 has the rotary element thereof mounted on the extended motorshaft 30 of an electric motor 3| that is mounted within the casing |2beneath the chute l4. This motor 3| also serves to impart rotativemovement to the drying drum l5 and this is accomplished through a.frictional drive that includes a friction wheel 32 on the other end ofthe shaft 30, a frictional wheel 33 engaging the friction wheel 32, ashaft 34 upon which the wheel 33 is mounted, and a pair of pulleys 35.The two pulleys 35 are supported so as to be disposed beneath theforward edge of the drum II, and on opposite sides of a vertical planepassing through the axis of the drum. One of the pulleys is supportedin-such a way that the upper run "U of the belt frictionally engages andsupports the forward edge portion of the drum l5, thereby to drive thedrum.

The duct or passage 26 through which the drying air is forced by the fan25 is formed at its lower side by the lower wall of the casing l2 whilethe upper wall of this passage is afforded by the lower wall of theinner casing 20. Between such upper and lower walls, a rear wall 26R anda front wall 26F are extended so as to thus define the air passage 26,and the burner and control unit II is placed in position within thepassage 26 through a relatively large clearance opening that is formedin the front wall 26F of the passage. Under the present invention theunit I.

is assembled on and carried by a mounting plate assembly 4| whichpreferably comprises an outer metal plate 4|M and a relatively thickinner or rear plate 4|P formed from an electric insulating material. Theplate assembly 4| serves to cover 4 the opening 4|, and the mountingplate assembly 4| is removably secured in position by means such asscrews 42.

The burner unit ll includes a burner structure 5 44 that is shown indetail in Figs. 3 to 6 of the drawings, and as there shown, the burnerunit 45 includes an elongated cylindrical burner tube 46 having aplurality of air inlet openings 41 formed therein and spaced thereaboutand throughout 10 the length of the burner tube. At its rear or lefthand end as viewed in Fig. 3, the burner tube 4 has a cross wall 48secured therein as by welding. and a gas supply fitting 49 has anelongated nipple 58 formed thereon and threaded through the 1 cross wall42. The nipple ill has an elongated passage 5| formed axiallytherethrough and at its rear or left hand end, and as shown in Fig. 3,this passage 5| opens into a relatively large chamber 53 that is formedin the fitting 4!. Gas is sup- 20 plied to the chamber 53 through a pipe54, and the rate of discharge through the passage SI and into the burnertube 48 is governed by an adjustable needle valve 55 which may be heldin adjusted position by a lock nut 56.

For the purpose of igniting the fuel that is thus supplied to the burnertube 40. a spark plug 54 is threaded into an opening "A, Fig. 7, in thetube 46 Just ahead of or to the right of the discharge end of the fuelpassage Si, and this spark plug 30 58 is energized as will hereinafterbe described when the burner 45 is to be lighted.

In order that the burner 45 may operate safely and efiiciently withinthe rapidly moving current of air in the duct 26, an air control sleeveCl is 5 operatively associated with the burner tube 48 so as to controland direct the supply of air to the burner tube 48, The control sleeve Nis somewhat larger than the sleeve 46 so as to be spaced radially.therefrom, and at its forward end, and at the 40 right in Fig. 3, withrespect to the openings 41, an

annular closure wall 6|. is disposed between the two sleeves 46 and illso as to maintain the same in concentric relation while at the same timepreventing right hand or forward discharge of air 45 from the spacebetween the two right hand ends of the sleeves 46 and ill. At the rearor left hand ends of the sleeves or tubes 46 and 60 the desiredsupporting connection is aflorded by a pair of relatively narrow metalbrackets 63 that are of a U-shaped form. These brackets are disposed atdiametrically opposite points, and one arm of each bracket is secured asby welding at 64 to the burner tube 46. The other arms of the brackets63 are arranged to engage oppositeoutside faces of the control sleeveGil, and are secured to the sleeve by means such as screws 65.

The assembly that is thus afforded is supported on the rear or the innerface of the mounting plate assembly 4| by a rearwardly projecting 60bracket 68 which has rearwardly projecting arms 68R that are of arcuateshape so as to embrace the air control sleeve 60, and these arms aresecured to the control sleeve by means such as screws 69. The bracket 68has forward arms 68F 5 that are secured against the inner or rear faceof the mounting plate assembly 4| by means such as screws 10. It will beobserved in this connection that the burner 45 is supported on themounting plate 4| so that the axis of the burner is sub- 70 stantiallyhorizontal and the relationship is such that the end 58E of the sparkplug 58 extends through an opening 12 in the mounting plate assembly 4|so that this end 58E of the spark plug is available for the attachmentof the nec- 76 essary electrical connection thereto. Furthermore, thesupply pipe 84 through which gas is supplied to the burner extendsforwardly through the opening I8 in the mounting plate assembly 4|, andas will become apparent as the description proceeds, this enables thecontrol means to be assembled on the forward face of the plate assembly4I so that the unit may be put in position by rearward movement of theplate assembly 4| into such a position that the mounting plate assembly4| covers the opening 48 in the supply duct 26. In Figs. 3 and 5 of thedrawings, it will be observed that a relatively small vent pipe I8 isextended through the mounting plate 4| and through openings I8 and 11 inthe sleeves 88 and 48 respectively, and the function of this vent pipewill hereinafter be apparent.

In the use of a gas burner in installations such as a domestic clothesdrier, it is essential that complete or substantially completecombustion be attained, and it is also essential that safety controlmeans be afforded for shutting off the gas supply in the event of aflame failure. In

the accomplishment of these two essential functions, the burner unit I8of the present invention has means mounted on the inner or rear face ofthe plate assembly H in positions where they will cooperate with a flameF or with the gaseous fuel that issues from the burner 45 as indicatedin dotted outline in Fig. 3. Thus in Figs. 3 and 6, it will be evidentthat a pair of insulating mounting structures 88 .are aiforded atvertically spaced points so as to extend through the mounting plateassembly 4I just forwardly or to the right of the right hand end of theburner 45. Each structure 88 comprises a pair of elongated hollowinsulators 88F and 88R disposed on opposite sides of the plate assemblyM in alignment with opposite ends of a clearance opening 88H in theplate assembly 4|. A rigid rod 82 extends through each pair ofinsulators 88F and 88R, and nuts 82F and 82B on the rod 82 engage theseinsulators so as to clamp the same against opposite sides of the plateassembly 4|. At their inner ends the rods 82 are bent toward each otheras at 82A, and between the ends of the arms 82A, a sensing ring R issecured as by welding the ends of the arms 82A to opposite outsidesurfaces of the ring R at 83. The ring R is supported in such a relationthat it will be enveloped in the outer border portions of the flame F asshown in Fig. 3, thereby to assure efllcient electrical contactbetween-the flame and the ring R. Just beyond the ring R, or to theright as viewed in Fig. 3, a wire mesh member 86 is supported in anormal relation to the axis of the bumer 48 and is substantiallycentered upon such axis. The wire mesh member 85 is preferably square inform, and is of such width that the flame from the burner 45 may spreadand pass about the wire mesh member 85. As herein shown, the wire meshmember 85 is supported on a bracket 86 that is welded at its rear end toone edge of the member 85 and is secured by screws 81 at its forward endto the rear face of the insulating plate HP. The location of the meshmember 86 so that the gaseous fuel may pass about the edges thereofassures that combustion will take place on both sides of the wire meshmember, and the heating of the wire mesh member 85 is such that thismember serves as a re-ignitor to insure that complete combustion of thefuel gas will take place.

It has been found that with the burner 48 constructed in the manner thusdescribed, the supply of air to the burner is initially limited by theinlet end opening of the flow directing sleeve or tube 88 and thislimiting control is attained even though the main stream of air throughthe passage 28 is moving quite rapidly. The primary air for supportingcombustion that is thus limited in its initial volume, is thenredistributed evenly within and throughout the inner burner tube 48 byvirtue of the inlet openings 41, so that the combustion may progress andbecome well established within the tube 48. and this produces emcientcombustion in the flame F as it is proiected from the tube 48 and pastthe sensing ring R and the ignitor 88. With this arrangement thecombustion is sustained even in the rapid current of air that passes thebumer and hence efllcient heating of such air is attained.

The supply of fuel gas to the burner 45 is soverned by a sensitivecontrol valve 88 which is of the construction shown in Figs. 8 and 9 ofthe drawings. This control is of a conventional construction in mostrespects and may be identified as a type B-'60 gas valve made by GeneralControls Company of Glendale, California. This control valve 88 has avalve casing comprising a base casting 8|, a head casting 82 secured inposition on the base casting 8| by means such as screws 88, and a capmember 84 of an inverted cup-shaped form that is secured on the top of'the head section 82 by means such as screws 85. The base casting 8i hasan inlet 86 formed therein and a supply pipe 81 is threaded into thisinlet. At the opposite edge of the base casting, an outlet 88 isafforded into which the pipe 54 is threaded so that the valve 88 issupported by the pipe on the mounting plate assembly 4 I and forms apart of the burner unit assembly I8. A horizontal web 88 and a verticalwall I88 formed in the base casting serve to afford a mounting for anannular valve seat member I M that is disposed in the web 88 on avertical axis. The upper edge of the valve seat member IN is adapted tobe engaged by a valve seat member I82 01' disc-like form so as tothereby prevent flow of gas through the valve, and the valve member I82is fixed on the lower 45 face of a flexible diaphragm I88 that isclamped in a horizontal position between the upper face of the basecasting 8i and the lower face of the head section 82. A relatively largedisc I84 is secured on the upper face of the diaphragm I88 58 to serveas a weight which tends to close the valve. It will be evident, however,that the gas pressure in the inlet passage 96 tends to open the valve,or in other words, to actuate the diaphragm I 88 so as to lift the valvemember I82 off of its annular valve seat I8I.

Under normal conditions, however, gas pressure is transmitted from theinlet 86 to a chamber I85 that is formed within the head casting 82, andthus the pressures on opposite sides of the so diaphragm are equalizedso that under the then dominating action of the weight I84, the valvemember I 82 assumes its lower or closed position. Thus. as will beevident in Fig. 9, a bleed passage I86 is formed from the inlet passage86 so as to 85 extend upwardly through the clamping edge portion of thediaphragm I 83 and through a vertical passage I86A in the head section82. The passage I86A communicates with a horizontal passage M1 in thehead section 82 and the gas from the pas- 7 sage I81 is discharged intothe chamber I85 through a nozzle I88 that is fitted into the horizontalpassage I81.

It will be observed in Fig. 9 that another nozzle I88 is mountedhorizontally and in alignment with the nozzle I88. and a flapper valve II8 is disamass use between the two males m and m for rocking movement ona horizontal axis III into closing engagement selectively with either ofthese two nozzles. An expansiv spring II2 acting on tht lower endportion of the flapper valve I II normally tends to engage the flappervalve II. with the vent nozzle IIII, it being noted that the nomle Illcommunicates through a passage III and a fitting I I4 with the vent pipeII. Thus, since the nozzle lilis thus normally closed, the gas pressurefrom the inlet 98 may build up a corresponding pressure on the upperside of the diaphragm, so as to cause the valve I02 to close. When thevalve member I42 is to be moved into its open position, the flappervalve III is rocked in a clockwise direction so as to close the nozzleIll and open the vent nozzle III.

This serves to close the pressure equalizing passage from the gas inlet88 and at the same time to open the vent nozzle Ill and thereby causereduction of the gas pressure above the diaphragm I". It will beobserved that the gas that is thus vented is contained within thechamber Ill and within the cap 94, the interior of which communicateswith the chamber I", as will be evident in Pig. 9.

The operation of the flapper valve I Il-requires but very little energy.and this is accomplished magnetically thsough an operating coil I I5.This operating coil is wound upon the upper arm INA of a U-shaped coreiron member II, the lower arm IIiB of which is in contact with theflapper member III at substantially the pivot III. The upper end I IIAof the flapper member is disposed opposite the end of the upper arm IIIAof the core member so that when the operating coll III is energized, theflapper member I ill will be magnetically shifted in a clockwisedirection from the position shown in Pig. 9 to a position where thenozzle III! is closed and the nozzle II! is open. As hereinabove pointedout. this valve structure is conventional in substantially everyrespect, the coil Ill, however, being rewound in the present instance tomatch the same with an energizing control source as will presently bedescribed.

The gas that is thus vented from the chamber III whenever the valvemember I42 is open, represents a relatively small volume of fuel, and,in many instances, where valves such as the valve .0 are utilized, thissmall volume of fuel gas is merely vented to atmosphere. However, weprefer to vent this gas into the burner 45 and this is accomplishedthrough the vent pipe which is extended from the fitting I I4 0 as toterminate. as shown in Fig. 3, within the burner sleeve 4'.

The operation of the fuel valve 94 is governed by a burner safetycontrol system I20, Fig. 10, which includes an electron tube I2I, andthe power for the control system I as well as for the driving motor 3|is controlled by a common thermostatic switch means which operates tostop the cycle of operation of the machine upon completion of the dryingcycle. Thus, in Fig. 10, a source of alternating current is afforded bywires LI and L2, through an overload switch I28. The overload switch I26is connected by a wire I21 to one terminal of a combination starting andthermostatic cut-out switch I28, the other terminal of which isconnected to the wire LI. The combination starting and thermostaticswitch 128 is of conventional construction and the thermostatic elementthereof is mounted in association with the air outlet e 29,1"ig. i, soas to open the switch I2! when thetemperaduetocompletionofthedryingaotionuponthe clothes in themachine.Thus, when the machine is to be started. the switch I24 is closed so asto thereby start the motor 2|, and the control system I2|| is arrangedto be supplied with power only during the time when the switch I24remains closed.

The control system I24 includes means for affording the necessary powerand bias for the electron tube III, and in the present instance suchmeans comprise an autotransformer III having sectional windings definedby terminals I2I, I32, I23 and I14. The tube III and the transformer IIIare mounted on the forward face of the plate 4I, thereby to form a partof the unit II which is assembled on the plate H. The chassis I24 servesas an enclosure and mounting for the various electrical element of thecontrol circuit. The terminals Ill and I22 are disposed at opposite endsof a section Ill-I of the transformer winding, the terminals I22 and Illare disposed at opposite ends of the winding section 4-2 while theterminals I23 and I34 are disposed at opposite ends of a section ISO-2of the transformer winding, such sections of the transformer windingbeing in series so that the terminals III and I24 are at opposite endsof the complete winding. The terminal IlI is connected by a wire Ill atthe junction between the wires I24 and I25, while wires I31, I38, andIII, in a series, connect the terminal I82 with the line wire L2. Thuswhen the switch I2! is closed, the transformer winding is energized, andthe line wires are connected so as to aiford plate circuit power for theplate circuit of the electron tube |2I, as will now be described. Thiselectron tube I2I may take the form of a type 2D2l Thyratron, and thistube has an anode I44, a cathode I, a shield grid I42, and a controlgrid I43. The tube also has a heater filament I44. The cathode I or thetube is connected by a wire I44 to the wire III, while the anode orplate II is connected to one terminal of the operating coll III of thevalve 90, the other terminal of this coil being connected by a wire I44to the terminal III of the transformer Ill. The operating coil II! ofthe fuel valve 4. is thus included in the plate circuit of the tube I2I,and the coil II! will be energized whenever plate current flows in theplate circuit of the tube I2I.

The energizing circuit for the filament I44 is afforded by connectingthe same across the section Ii-2 of the transformer, and for thispurpose a wire I44 extends from the wire I" to one terminal of thefilament I44, while the other terminal thereof is connected by a wireI48 to the terminal Ill.

The tube I2I is normally biased to a non-conductive state by biasvoltage applied to the shield grid I42, and when the tube I2I is to berendered conductive, an appropriate positive voltage is supplied to thecontrol grid I42 as will hereinafter be described. In affording thedesired negative or blocking bias for the shield grid I42, a wire I50, aresistance III and a wire I53 are extended in a series from the terminalI34 to the shield grid I42. Thus the negative voltage from the terminalI34 which is more negative at the critical time than the cathode voltagetaken from the terminal I32, is applied to the shield grid I42 in whatmay be termed the positive cycles of the alternating current or, inother words, in those cycles when the plate I 4| ture of the outgoingair becomes unduly high 14 is positive with respect to the cathode I,and

the magnitude of the negative bias that is thus afforded is such that inthe absence of an appreciable positive potential on the control-aridI43, the tube I2I will be non-conductive. Moreover, even when the ,tubeIII is conductive, the most common failure that may occur in the tube,which failure involves burning out of the filaconductive so as to resultin what is usually termed a "safe failure.

When the switch I28 is closed so as to thereby start the motor 3|, theburner operation is not initiated or started until a separate startingswitch means in the form of a starting button I80 is operated. Thestarting button I80 is arranged as will hereinafter be pointed out tocause the tube I2I to become conductive, so as to thereby open the fuelvalve 80 and also to cause the ignition means which include the sparkplug 83 to be energized. Thus, in the form disclosed in Figs. 1 to 10.an'ignition transformer I8I is mounted on the forward face of the plate4I immediately beneath the spark plug 53. The transformer I8I has asecondary coil IBIS and a primary coil I6IP. The secondary coil I8IS hasone terminal grounded at I82 while the other terminal thereof isconnected by a wire I83 to ment I44, will cause the tube to becomenonthe spark plug 58. The other side of the spark plug 58 is, of course,grounded to the burner 46 and this ground connection is indicated inFig. 10 at I64. The primary coil I8IP has one terminal thereof connectedto the wire I38, while the other terminal thereof is connected to astationary switch contact I65 of the switch I60. A cooperatingstationary contact I66 of the switch I80 is connected by wires I81 andI88 to the wire I48, and a conducting cross arm I83 on the switch I60may thus be engaged with the contacts I85 and I66 to energize theignition transformer I6I. The switch I80 also has a second conductingcross bar I10 that may be engaged with stationary contacts I" and I12when the starting button I60 is pressed. and these contacts areeffective, as will hereinafter be described, to apply positive voltageto the control grid I43 so as to thereby cause the fuel valve 80 to beopened. In attaining this action, the switch means afforded by the barI10 and the contacts I'll and I12 completes a circuit which effectivelysimulates the presence of a flame at the burner 45, and for this reasonthe normal action of the control system will first be described.

The flame sensing ring R is arranged and associated with the electrontube I2I in such a way that when a flame is present so as to extendbetween the burner 45 and the flame sensing ring R, a positive voltagewill be applied to the control grid I43 so as to render the tube I2Iconductive. In attaining this result, the burner 45 is connected to theline wire L2 by a resistance I15 and the wires I38 and I39. The flamesensing ring R in turn has a wire I16 extended from one of the rods 62to one end of a resistor I11, the other end of this resistor beingconnected to a resistor I18.

The other end of the resistor I18 is connected to the control grid I43.At the juncture of the resistors I11 and I18, one terminal of acondenser I80 is connected at the juncture of the wires I81 and I68.

When a flame F extends between the burner 45 and the flame sensing ringR, a circuit is completed through the flame F and the resistance of theflame constitutes a circuit element of a circuit that extends fromground at I84, or cathode poforth, this voltage on the control I43 maybe made effective to cause the tube I2I to become conductive. In thestarting operation, this action is attained throughthe switch bar I10,the contact I12 being connected by a wire I8I to the burner 45 while thecontact I" is connected through a resistor I82 to the wire I18. Astabilizing condenser IBM. is connected between the grid I43 and thewire I31 so as to produce uniformity of operation.

In setting up the control thus described, the following values for thevarious circuit elements have been found to be satisfactory:

Condenser I80A .00015 microfarad Condenser I80 .0005 microfaradResistance I5I 50,000 ohms Resistance I18 1.5 megohms Resistance I11 1.0megohm Resistance I15 2,000 ohms Resistance I82 7 megohms When dryer isto be started, the start switch I 23 is moved to its closed and latchedposition so as to thereby start the motor 3| and energize thetransformer I30. The connections from the transformer section I30-2serve to heat the cathode I4I, while the negative bias applied to thescreen grid I42 serves to block the tube I2I and prevent flow of platecurrent therein. In this respect it should be noted that prior to thestarting or ignition of the burner 45, the only power connection to thecontrol grid I43 is through the condenser I80 and the resistor I18 fromthe side of the transformer winding that is connected to the anode.Under such circumstances there is no current flow through the condenserI 80, for although one side of the condenser is connected to the sameterminal of the transformer I30 as the anode I40, the other side of thecondenser I80 may be said to be floating because all of the circuitbranches from such other side of the condenser I80 are at this time inan open circuit relation. Thus the switch bar I10 of the start switch isin an open relation, while the. branch through the flame sensing ring Ris open due to the lack of a flame F. The other branch circuit throughthe resistor I18 to the control grid I43 is also open, since the tube isblocked by the highly negative shield grid bias, so that there is noflow of cathode-grid current. Moreover, the impedance of the stabilizingcondenser I80A is high so that there is no current flow therethroughandthe effect is the same as an open circuit at this point. Thus,although one side of the condenser I80 is connected so as to be positivein those half cycles when the anode or plate is positive, the lack ofcurrent flow, or the extremely small current flow across the condenser I80 in such forward half cycles, assures that positive grid bias will notbe applied to the control grid at this time.

As a result of this circuit arrangement'the tube I20 remainsnon-conductive until such time as the start button I 60 is actuated.This, of course, operates the ignition means so as to produce ignitingaction at the spark plug 58, and in addition, a circuit is closed fromthe ground side of the line through the resistors I81 and I11'and thecondenser I80 to the hot side of the line. In this assaoss llrespectitmaybenotedthatthevaluecftheresister Iflis suchastosimulatethereaistance'ofa flame between the burner ll and the sensing ring R, andhence'the effect on the bias of the control grid I" is the same as whena flame is sensed. Thus the circuit that is established between the linewires LI' and L2 includes the condenser III. the resistance I", and theflame-simulating resistance I", and this circuit acts as a voltagedivider frmn which the control grid bias is tapped through the limitingresistor Ill. The point at which the control grid is thus tapped is suchthat the grid I is rendered sufficiently positive to cause firing of thetube Iii throughout a substantial portion of each forward cycle so longas the resistance in the voltage dividing circuit is kept within acertain range.

Whentheflringofthetube III inresponsetc operation of the start button Ihas caused opening of the fuel valve III, and the fuel fed to the burner40 has been ignited, the presence of aflamel'willbesensedbythesensingringR. This completes a circuit that isin parallel with the resistor I02 and which includes the resistance ofthe flame 1'' and at this time the start button Ill may be released soas to place the system under sole control of the flame sensing means.The flame resistance has been found to vary from about two to seventymegohms, and throughout this range,'the voltage dividing network will beeffective to maintain a flring bias on the control grid I. If, however,the flame F is extinguished. or if the sensing ring it becomes grounded,the positive bias voltage on the control grid I will be reduced orchanged in such a way as to enable the negative bias of the shield gridI42 to regain control and render the tube III non-conductive. In thecase of a grounding of the sensing ring,

coilwinding.'1hesectionofthesparkcoilwindingbetween the taps I and Illconstitutes the secondary,andthetapilliseonnectedbyawire ill to thespark plug ll while the tap! is grounded at 212. with the structure thusafforded, thea'equired ignition means functions inahighlysatisfactorymanncnandyetmaybe provided at a reasonable cost.

The values specifled hsreinabove for the circuit I elements are ofcourse what we wnsider to be optimum values, but it will be recognisedthat suchvaluesmayvarywithincertainlimi while-,theresistanceslllandi'llmaybecombinedand placed between the condenserIll and the control grid I. when this is done, the flame constitutes thesole resistance for cooperation in serieswiththecondenserlllinaflordingthevoltage dividing network from which the control gridvoltage is tapped.

From the foregoing description it will be evident that the presentinvention enables -a gas burner to be safely utilised in a rapidlymoving current of air such as the air that is forcedthroughaclothesdrierorthelikc.andthisisaccomplished through the use ofstructure that is extremely simple in character. Moreover, it will beevident that the present invention aflords a burner and control assemblyof a simple character that may be easily and economically manufacturedand serviced.

the resistance at the flame gap is reduced to zero so that the effectiveposition of the control grid tap will be so changed in an electricalsense as to reduce the control grid bias to such a point that it isbelow the positive value required to flre the tube, and hence the shieldgrid I 42 will regain control in the next inverse cycle.

Flame failure willof course return the system to its original conditioninsofar as biasing voltage on the control grid I" is concerned, andhence the shield grid will resume control, and the tube will becomenon-conductive. In either event, the valve III will be de-energized, andwill close so as to shut off the supply of fuel to the burner 45.

In Fig. 11 of the drawings an alternative form of ignition means hasbeen illustrated whereby the use of a relatively expensive ignitiontransformer IOI may be avoided and in this embodiment of the invention aspark coil ill of substantially conventional construction is utilized.The spark coil 2" is auto-wound to aflord a winding 2" having terminals203, I and 285, and a contact-2" extended from the terminal 2" has avibrating armature contact 2'1 associated therewith to act in the usualmanner as a periodic circuit breaking means. The contacts 208 and I"have a condenser 26! connected thereacross, and the contact 201 isconnected to the contact I of the start switch I60. The other contactI80, instead of being connected to the wire I01, is connected by a wire2" to the wire Ill, and another and separate winding section I 8H thatis afforded in the transformer I ll to afl'ord the usual 8-volt sourcefor the spark coil "I. A wire I'll extends from the other endofthewinding nHmmeta monthesperk.

Thus, while we have illustrated and described the preferred embodimentsof our invention. it is to be understood that this is capable ofvariation and modification and we therefore do not wish to be limited tothe precise details set forth, but desire to avail ourselves of suchchanges and alterations as fall within the purview of the follow- 1118claims.

We claim:

1. In a burner and control unit for heating air moving longitudinallythrough an elongated passage. a mounting plate having inner and outersides and adapted to be put in position over an opening in the side ofsuch a passage, an elongated burner tube structure having front and rearends and supported on said plate opposite and in spaced parallelrelation to said inner side thereof. a gas inlet fitting mounted on therear end of said burner tube structure for supplying gaseous fuelthereto, a supply line for said fitting extended through said plate, acontrol valve connected to and supported by said supply line ad- Jacentthe outer side of said plate. a spark plug mounted on said burner tubestructure and having the power supply end thereof extended through saidplate, a flame sensing element mounted on the inner side of said platein alignment with but spaced from the front end of said burner structureand positioned so as to be enveloped in a flame issuing from said burnerstructure, a re-ignitcr comprising a metallic screen mounted on saidinner side of said plate in beyond said sensing element and in positionto be enveloped by such a flame. and control means mounted on the outerside of said plate and operatively associated with said sensing element584d valve for controlling the opening and 13 closing of said valve inaccordance with the sensing action of said sensing element.

2. In a burner and control unit for heating air moving through alongitudinal passage, a mounting plate .having inner and outer sides andadapted to be put in position over an openingin the side of such apassage, an elongated burner tube structure having front and rear endsand supported on said plate opposite and in spaced parallel relation tosaid inner side thereof, a gas inlet fitting mounted on the rear end ofsaid burner tube structure for supplying gaseous fuel thereto, a supplyline for said fitting extended through said plate, a control valveconnected to and supported by said supply line adjacent the outer sideof said plate, a spark plug mounted on said burner tube structure andhaving the power supply end thereof extended through said plate, a flamesensing element mounted on the inner side of said plate in alignmentwith but spaced from the front end of said burner structure andpositioned so as to be enveloped in a flame issuing from said burnerstructure, a reignitor comprising a screen mounted on said inner side ofsaid plate in beyond said sensing element and in position to beenveloped by such a flame, control means mounted on the outer side ofsaid plate and operatively associated with said sensing element and saidvalve for controlling the opening and closing of said valve inaccordance with the sensing action of said sensing element, normallyinoperative power supply means for said spark plug, and a start elementadapted to be moved to a start position and adapted to govern saidcontrol means to open said valve and also to cause operation of saidpower supply means for said spark plug.

3. In a burner and control unit for heating air moving through alongitudinal passage, a mounting plate having inner and outer sides andadapted to be put in position over an opening in the side of such apassage, an elongated burner tube structure having front and rear endsand supported on said plate opposite and in spaced parallel relation tosaid inner side thereof, a gas inlet fitting mounted on the rear end ofsaid burner tube structure for supplying gaseous fuel thereto, a supplyline for said fitting extended through said plate, a control valveconnected to and supported by said supply line adjacent the r elementmounted on the inner side of said plate in aignment with but spaced fromthe front end of said burner structure and positioned so as to beenveloped in a flame issuing from said burner structure, and controlmeans mounted on the outer side of said plate and operatively associatedwith said sensing element and said valve for controlling the opening andclosing of said valve in accordance with the sensing action of saidsensing element.

4. In a burner and control unit for heating air moving through alongitudinal passage, a mounting plate having inner and outer sides andadapted to be put in position over an opening in the side of such apassage, an elongated burner tube structure having front and rear endsand supported on said plate opposite and in spaced parallel reation tosaid inner side thereof, a gas inlet fitting mounted on the rear end ofsaid burner tube structure for supplying gaseous fuel thereto, a supplyline for said fitting extended through saidplate, a control valveconnected to "and supported by said supply line adjacent the outer sideof, saidplate, a flame sensing element mounted on the inner side of saidplate in alignment with but spaced from the front end of said burnerstructure and positioned so as to be enveloped in a flame issuing fromsaid burner structure, and control means mounted on theouter side ofsaid plate and operatively associated with said sensing element and saidvalve for controlling the opening and closing of said valve inaccordance with the sensing action of said sensing element.

5. In a burner and control unit for heating air moving through alongitudinal passage, a mounting plate having inner and outer sides andadapted to be put in position over an opening in the side of such apassage, an elongated burner tube structure having front and rear endsand supported on said plate opposite and in spaced parallel relation tosaid inner side thereof, a gas inlet fitting mounted on the rear end ofsaid burner tube structure for supplying gaseous fuel thereto, a gassupply line for said fitting extended through said plate, a controlvalve connected to and supported by said supply line adjacent the outerside of said plate, and a flame sensing element mounted on the innerside of said plate in alignment with but spaced from the front end ofsaid burner structure and positioned so as to be enveloped in a flameissuing from said burner structure.

6. In a burner and control unit for heating air moving through alongitudinal passage, 9. mounting plate having inner and outer sides andadapted to be put in position over an opening in the side of such apassage. an elongated burner tube structure having front and rear endsand supported on said plate opposite and in spaced parallel relation tosaid inner side thereof, a gas inlet fltting mounted on the rear end ofsaid burner tube structure for supplying gaseous fuel thereto, a gassupply line for said fitting extended through said plate, a controlvalve connected to and supported by said supply line adjacent the outerside of said plate, a flame sensing element mounted on the inner side ofsaid plate in alignment with but spaced from the front end of saidburner structure and positioned so as to be enveloped in a flame issuingfrom said burner structure, and ignition means mounted in part on theouter side of said plate and having spark gap elements operativelyassociated with said burner structure on the inner side of said plate.

7. In a burner and control unit for heating air moving through alongitudinal passage, a mounting plate having inner and outer sides andadapt ed to be put in position over an opening in the side of such apassage, an elongated burner tube structure having front and rear endsand supported on said plate opposite and in spaced parallel relation tosaid inner side thereof, said burner tube structure having air inletopenings in said rear end thereof for admitting a controlled volume ofair from the air moving through such a passage, a gas inlet fittingmounted on the rear end of said burner tube structure for supplyinggaseous fuel thereto, a supply line for said fitting extended throughsaid plate, a control valve connected to and supported by said supplyline adjacent the outer side of said plate, and a flame sensing elementmounted on the inner side of said plate in alignment with but spacedfrom the front end of said burner structure and positioned use:

15 so as to be enveloped in a flame issuing from said burner structure.

ROBERT E. YATES. JOSEPH M. ENGEL. WILLIAM W. RIESCHE. 5

REFERENCES CITED The following references are of record In the file ofthis patent:

Number 10 UNITED STATES PATENTS Name Date Randol Apr. 21, 1885 Good Oct.11, 1921 Bluemel June 14, 1932 Crary Sept. 27, 1938 Plein et a1. Dec. 8.1942 Kruae Dec. 24, 1946

